1. Field of the Invention
This invention relates to a camera which can be loaded with film having a magnetic recording portion.
2. Related Background Art
A camera which uses film having a magnetic recording portion in which data such as dates, shutter speeds and aperture values can be written into the magnetic recording portion and from which, as required, these data can be read out along with data such as pre-recorded film speed and the prescribed number of film frames is disclosed in U.S. Pat. No. 4,864,332, etc.
Also, a camera in which when photographing data such as shutter speed and aperture value and date data are recorded onto the magnetic recording portion after the photographing by the camera, the information that the film has been exposed is also recorded on the film simultaneously therewith and the partially exposed film is rewound so that when the film is to be reused in the same camera or a different camera, the heading of the film is effected on the basis of said information to enable the exposure of unexposed frames to be accomplished is proposed in U.S. Pat. No. 4,878,075.
Also, a camera which uses a film cartridge containing all of a film (including the leader portion thereof) therein and in which a supply spool in the film cartridge is rotated to thereby force the leader portion of the film out to the film take-up spool side of the camera is proposed in U.S. Pat. No. 4,834,306.
However, in the above-described examples of the prior art, the reading-out of the data such as the film speed pre-memorized in the magnetic recording portion of the film is effected only during the feeding of the film in one direction, such as the film, winding after the loading of the film and therefore, depending on the difference between individual cameras or the non-uniformity of film, the recording track on the film and the magnetic head of the camera sometimes do not contact each other accurately, and a magnetic signal sometimes cannot be read out due to an azimuth error caused by the head gap and the inclination of the recording track or to the off-track alignment caused by the positional deviation between the magnetic head and the recording track.
Also, there are cameras of two photographing types, i.e., the pre-wind type and the normal wind type, but when in the camera as disclosed in the above-mentioned U.S. Pat. No. 4,878,075, an attempt is made to effect photographing and data recording by a camera of the normal wind type up to an intermediate frame of film, and thereafter effect photographing and data recording on the subsequent frames by a camera of the pre-wind type, there occurrs the error as noted above.
When the data such as the film speed cannot be read out as described above, usually all the film is rewound to make photographing onto the film impossible and thus, the film was wasted.
Also, in the above-described examples of the prior art, the reproduced state of magnetically recorded data changes depending on the difference in the feeding speed, the difference between cameras, the difference between films, or the like, and this leads to the problem that the magnitude or frequency of a signal changes greatly. Also, the magnetic layer must be made thin in order to provide the film with a magnetic recording portion and therefore, the signal level unavoidably becomes small. Further, because of the necessity of effecting reproduction during the feeding of the film, the noise of a motor becomes greater as the load of the film becomes greater, and this poses the problem that the reproduction signal is deteriorated in S/N and the signal could often cannot be read.
Also, in the above-described examples of the prior art, when magnetic recording and reproduction cannot be effected, it cannot be judged whether there is no magnetic recording portion on the film, whether magnetically recorded data written by another camera is bad, or whether the reproduction circuit of the camera is bad. In some cases, this may be judged to be a problem and thus, there is the possibility that the camera no longer functions as a camera. That is, in the above-described examples of the prior art, no mention is made of any countermeasure for a case where a problem has occurred with magnetic recording means including a magnetic head for writing data onto the magnetic recording portion of the film, and it is generally considered that when a problem has occurred with the magnetic recording means, such trouble is regarded as a bad photographing operation, such as a bad shutter operation or a bad lens barrel operation of the camera, and the camera is rendered inoperative. However, if such a camera is constructed, there will arise the problem that photographing cannot be effected at all in spite of the fact that in The case of the problem with the magnetic recording means, it is possible to effect exposure on the film surface, except for the recording of data.
A technique whereby a film cartridge is endowed with the function of displaying the used state of film is proposed in Japanese Laid-Open Patent Application No. 3-6556.